1. Field of the Invention
This invention relates generally to microprocessor and microcontroller power supplies, and more specifically, to a power supply system having a programmable power supply and a programmable brownout detector which can be set to track the power supply output. The programmable power supply and the programmable brownout detector are independently controlled by a common, intelligent control unit. The control unit may also disable the programmable brownout detector.
2. Description of the Prior Art
Programmable power supplies and brownout detectors for microprocessors are known in the art. The use of microprocessors in battery powered equipment and in high reliability applications has produced the need to change operating voltages to reduce current consumption for low power and battery powered applications and to detect when the operating voltage drops below a predetermined level for reliability considerations.
A brownout is considered to have occurred when the incoming voltage available to the microprocessor has dropped to a level where the microprocessor should not continue operating, since errors or partly functional conditions may occur in the logic or storage elements. The brownout ends when the voltage has risen back above the brownout level. A hysteresis or latching scheme can be used to prevent oscillation at the brownout level.
A brownout detector detects when the operating voltage has dropped to just above the brownout voltage level and produces a signal to indicate to the microprocessor that a brownout is pending.
The brownout detector can reset or freeze the operation of the microprocessor to avoid improper operation. In a practical application, the microprocessor must be protected against brownout conditions that can cause the logic to enter unknown states and thereby corrupt the operation of the processor.
In the existing state of the art, these power supplies and brownout detectors are either not linked in operation at all, or are linked only by virtue of the reference voltage"" to the brownout detector being related directly to the operating voltage to the processor. Also there is no provision for lowering the operating voltage of a microprocessor during sleep mode to reduce current consumption.
The present invention improves upon these past techniques by providing a programmable power supply which can lower the operating voltage during sleep mode or as the application otherwise requires and a programmable burnout detector which can intelligently relate the operating voltage to a brownout level. This prevents improper operation due to the brownout level being set too high by an improper instruction or by firmware error. It also allows for a complex relationship between the operating voltage reference and the brownout detector threshold.
It is an object of the present invention to provide a programmable brownout detector and a programmable power supply for increasing the reliability of a microprocessor system.
It is an object of the present invention to provide a programmable brownout detector which cannot be misprogrammed to detect an incorrect brownout level for a given operating voltage.
It is another object of the present invention to provide a system which allows a programmable brownout detector to have a threshold optimally determined over a range of operating voltages which are programmable.
It is another object of the present invention to provide a system which reduces the operating voltage to a microprocessor during sleep mode to reduce power consumption.
In accordance with one embodiment of the present invention, a programmable power supply and a programmable brownout detector are provided. The power supply and the brownout detector are programmed by a control unit, which allows the brownout voltage and operating voltage to be varied independently.
In accordance with another embodiment of the present invention, a programmable power supply and a programmable brownout detector are provided where they are both programmed by a control unit and the control unit prevents improper programming by firmware or operating failures.
In accordance with another embodiment of the present invention, a programmable power supply and a programmable brownout detector are provided wherein they are programmed by a control unit and the control unit relates the operating voltage to the brownout level so as to optimize operation of the brownout detector.
In accordance with another embodiment of the present invention, a programmable power supply is provided wherein the operating voltage is lowered during sleep mode to reduce power consumption in sleep mode.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.